Field of the Invention
The present invention relates to a device in which an electrode of an element such as a capacitance-type transducer that is used in an ultrasonic conversion element and the like is electrically connected to a penetrating wire, and a method for manufacturing the same.
Description of the Related Art
In recent years, various elements (sensor and the like) have been manufactured by a micromachining technology. Many of these sensors are produced with the use of a semiconductor process. As for these elements, not only the element itself is required to be miniaturized but also the device including a mounting portion is required to be miniaturized. Until now, an electrode for being connected to a circuit board or a wiring board has been arranged in the periphery of an element in many cases, and an area including the mounting portion has become large. As for one method for solving such a problem, there is a method of forming a penetrating wire on a substrate, and electrically connecting a wire of an element on the surface of the substrate to a wire on the rear face of the substrate. Thereby, the electrode can be formed on the rear face of the substrate, and a device which is provided with the element and includes the mounting portion can be miniaturized.
As for the above described technology, Japanese Patent Application Laid-Open No. 2006-13330 discloses a method for producing a penetrating wire substrate in the case where a functional element such as a cantilever is formed on the penetrating wire substrate. In this production method, a substrate having a through hole formed therein is bonded to a support, through a bonding layer (film resist) which has been formed on the surface of a plated seed layer on the above described support. After the bonding layer in a region which is linked to the through hole has been removed, a columnar electrode of copper is formed in the through hole. Finally, the support provided with the seed layer and the bonding layer are separated from the penetrating wire substrate. In addition, Japanese Patent Application Laid-Open No. 2010-272956 discloses a manufacturing method in the case where a capacitance type ultrasonic transducer has been formed on a penetrating wire substrate as a functional element. In this manufacturing method, the through hole is formed on a silicon substrate, polycrystalline silicon which becomes a wiring material is formed in the inside of the through hole, and then a capacitance type element is formed.
However, in the production method of Japanese Patent Application Laid-Open No. 2006-13330, when the bonding layer (film resist) in the region which is linked to the through hole is removed, a residue of the bonding layer must not be formed in order that the plated seed layer is exposed. In addition, it is not easy to confirm that the bonding layer has been removed, because the bonding layer is formed in the inside of the through hole, and the bonding layer needs to be over etched when the bonding layer is removed. However, when an over etching period of time becomes long, it becomes difficult to control a quantity of the spread in a lateral direction of a portion to be removed. As a result, the electrode material needs to have many margins of the quantity of spreading in the lateral direction of itself, and there is the case where the element and the penetrating electrode portion cannot be arranged at high density. In addition, in the manufacturing method of Japanese Patent Application Laid-Open No. 2010-272956, when the penetrating wire is formed of the polycrystalline silicon, it is not easy to lower the resistance of the penetrating wire because the polycrystalline silicon has high resistivity. Even when copper has been used for the wiring material, the number of steps for polishing both faces of the substrate increases, and the cost occasionally results in increasing.